There have been widely used machine tools which perform machining while performing automatic tool replacement between a tool magazine and a main spindle. In such machine tools, swarf produced during machining may attach to a tapered portion of a tool or of a tool holder having a tool attached thereto and/or to a main spindle's seating face on which the tapered portion is seated. When machining is performed with the tool or the tool holder mounted to the main spindle while such swarf exists between the tapered portion and the seating face, the tapered portion may not come in proper tight contact with the seating face of the main spindle. The tool is therefore not precisely positioned. This may adversely affect the machining accuracy and, in some cases, damage the tool and/or the main spindle.
To solve this, conventional machine tools are provided with a tool tight-contact-state detector which detects whether or not a tool or a tool holder is mounted to a main spindle in tight contact therewith. Examples of such tool tight-contact-state detector for a machine tool are disclosed in Patent Documents 1 and 2.
Patent Document 1: Japanese Patent Application Publication No. Hei 10-225845
Patent Document 2: Japanese Patent Application Publication No. 2001-259906